Eleven years ago, when Nutanix announced AHV, my initial reaction was: This will fail.

The idea that someone could successfully introduce a new commercial hypervisor into the market seemed ridiculous.

But 11 years later, it has proven me wrong.

Despite this, AHV remains deeply misunderstood because of its uniqueness.

Most operating systems are stateful, meaning that the system’s state is stored within the OS, and when the server restarts, the OS retrieves its state from disk.

AHV, however, is stateless, and so?

Consider a VM. For example, with ESX, you can create a VM through the ESX console, and if ESX crashes, the VM’s state is saved on local disks that ESX reads to restart it.

Much of vCenter’s job is to monitor what’s happening in ESXi and respond to an environment that doesn’t match its expectations of what ESXi was doing.

With AHV, creating a VM requires accessing the cluster control plane, which runs on the CVM—a special VM that manages the cluster’s state. For more details, see The Nutanix Bible.

Thus, when the OS boots, the cluster control plane determines its state.

Why is this so powerful?

During a reboot, the control plane doesn’t need to determine what AHV considers to be running, nor does it need to stop or start processes.

More importantly, the AHV state can’t be out of sync with what the control plane believes.

This setup also significantly simplifies everything. Systems like ESXi or Linux require building a layered control plane on top of the OS’s control system. This layered system must interpret and respond to the actions of the underlying control plane. If it needs to stop or change something, it is at the mercy of the underlying controls.

Most of the time, this isn’t an issue because complex software, such as kubevirt or hostd, tries to reconcile conflicting control goals.

With AHV, that intermediary layer doesn’t exist.

This leads to the misunderstanding: AHV is stateless and can’t be directly compared to ESXi or Linux/KVM. Instead, you should compare it to ESXi + vCenter or Linux with something like OpenShift.

When you make this comparison, you realize that AHV provides a level of availability and control that’s unmatched.

For example, vCenter manages multiple clusters, and any single cluster can impact all workloads. If vCenter fails, it affects all workloads, necessitating the use of numerous vCenters, which in turn leads to vCenter sprawl and increased operational overhead.

With AHV, the boundary is a cluster. Each cluster is isolated from the others.

Thanks to Prism Central, it’s more feasible to run multiple workloads on separate, isolated clusters.

Because the AHV control plane is clustered, its availability is tied to the availability of Nutanix clusters, unlike vCenter, which runs as a single VM.

All of this is possible because AHV’s stateless design allows the creation of a cluster control plane with a small team, achieving something once thought impossible.